A feature, i.e. high speed data packet access (HSDPA), is introduced in the universal mobile telecommunications system (UMTS) Release 5 (Rel-5), so as to further improve a user equipment (UE) peak throughput and cell throughput. After the HSDPA is configured on a UE, one and only one high speed downlink shared channel (HS-DSCH) serving cell is configured to the UE, and all HSDPA physical channels of the UE are established only on the HS-DSCH serving cell, in this case, on the UE side, there is a high speed medium access control (MAC-hs) entity or an enhanced high speed medium access control (MAC-ehs) entity, used to perform receive data at a MAC layer, correspondingly, on a network side, a MAC-hs or MAC-ehs entity is also configured in the HS-DSCH serving cell to perform send HS-DSCH data at the MAC layer.
A feature, i.e. multiflow transmission (Multiflow), is introduced when the UMTS technologies evolve to Rel-11. This feature allows a configuration that a UE sends HS-DSCH data in multiple intra-frequency cells or multiple inter-frequency cells, which can improve experience of a cell edge user significantly. At best a maximum of Multiflow cells, i.e. four Multiflow cells, namely, Cell-1, Cell-2, Cell-3, and Cell-4, can be concurrently configured for a user at the same time, where the Cell-1 and the Cell-2 are at a frequency 1, and the Cell-3 and the Cell-4 are at a frequency 2. Among the Multiflow cells, one Multiflow cell is called an HS-DSCH serving cell or an HS-DSCH primary cell of the UE, another cell which has the intra-frequency with the HS-DSCH serving cell is called an HS assisting serving cell or assisting serving cell of the UE, another cell that has a same timing relationship as the HS-DSCH serving cell is called an HS secondary serving cell or a secondary serving cell of the UE, and another cell which has the intra-frequency with the HS secondary serving cell is called an HS assisting secondary serving cell or assisting secondary serving cell of the UE.
Processing of the MAC-hs/MAC-ehs in a process of an HS-DSCH serving cell handover is as follows.
In the protocol, both the MAC-hs and the MAC-ehs are used to process data transmitted on an HS-DSCH, and configuration information of the MAC-hs and the MAC-ehs is controlled by an RRC layer. On the network side, each cell has one MAC-hs/MAC-ehs entity. Main functions of the MAC-hs or the MAC-ehs include: flow control, scheduling/priority processing, a hybrid automatic repeat request (HARQ) function, and TFRC selection; the MAC-ehs entity is an enhanced entity as the MAC-hs entity, and an added function of the MAC-ehs entity is mainly segmentation of a MAC-ehs SDU. When the HSDPA is introduced in Rel-5, on the UE side, it specifies that only one MAC-ehs entity exists on the UE side and corresponds to the HS-DSCH serving cell.
In the prior art, movement of a UE may trigger a handover of an HS-DSCH serving cell of the UE, and possibly, along with MAC-hs/MAC-ehs reset. In Multiflow, multiple Multiflow cells may be under a same NodeB or different NodeBs, when the multiple Multiflow cells are under different NodeBs, two MAC-ehses are required on the UE side to separately process downlink data sent from each NodeB. A single frequency dual cell (SF-DC) mode in Multiflow is used as an example, because MAC-ehses corresponding to an SF-DC primary cell and an SF-DC assisting cell of the UE may change, the network side may initiate a MAC-ehs reset process according to a procedure in an existing protocol, and a radio network controller (RNC) may only instruct the UE to clear data buffered on the MAC-ehs corresponding to the primary cell and set the MAC-ehs to an initial status; while for processing of the MAC-ehs corresponding to the assisting cell, there is no specification or indication that the UE needs to clear data buffered on both MAC-ehses and concurrently set both MAC-ehses to initial statuses.
The MAC-hs/MAC-ehs reset action in the prior art may cause two problems: One is that the UE does not know how to process the MAC-ehs corresponding to the assisting cell after the handover, thereby leading to an abnormal behavior of the UE; and another is that, after the handover, the UE must clear the data buffered on both MAC-ehses and set the both MAC-ehses to initial statuses, because during the MAC-hs/MAC-ehs reset, all buffered data of the MAC-layer are lost, a retransmission at a higher level (for example, retransmission at a radio link control layer) must be triggered, and in this way, system performance may be affected (which is specifically manifested in a data service interruption, a call drop resulting from loss of downlink air-interface signaling, or the like). As a result, the reset action of the MAC-hs/MAC-ehs in the prior art affects user experience, such as unsmooth video playing and a sudden call drop during a call.